Separating clinically relevant sources of electrical activity in ECG signals

Abstract

This invention provides a fully automatic method and a system for detecting and classifying cardiac arrhythmias from a surface ECG record. The method defines four relevant parameters whose values are extracted from said ECG record. Clinically relevant conclusions are assigned to various combinations of the obtained values of said parameters. The method can be employed for detecting fetal QRS complexes from abdomen ECG of a pregnant woman.

The invention claimed is: 
     
       1. A method for detecting clinically relevant sources of electrical activity in an ECG signal record, comprising:
 i) providing said ECG signal record consisting of 12 or less lead signals which were produced by the heart of a human subject and noninvasively measured at a plurality of points on the skin of said subject during a predetermined time interval; 
 ii) removing noise, using a filter, from said ECG signal record outside a frequency range of 0.5 to 49.5 Hertz (Hz); 
 iii) identifying, in said ECG signal record, electrical activity associated with fetal QRS complex or with atrial electrical activity (AEA), creating a synthetic signal and using a modified linear combiner; 
 iv) determining at least parameters α and β, wherein α is R-R regularity, β is HR in said ECG signal record, and wherein said parameters are determined automatically from said ECG signal record; and 
 v) assigning to a combination of said parameters of step iv) a clinical state according to a clinically oriented set of rules. 
 
     
     
       2. A method according to  claim 1 , for detecting and classifying cardiac arrhythmias comprised in the ECG signal record, wherein:
 step iii) comprises identifying atrial electrical activity (AEA) in said ECG signal record; 
 step iv) comprises determining parameters α, β, γ, and δ, wherein γ is a position of the delineated AEA wave relative to a QRS complex in said ECG signal record, and δ is a ratio of the delineated AEA wave and the QRS complex; and 
 step iv) comprises assigning to a combination of said parameters α, β, γ, and δ an arrhythmia type according to the clinically oriented set of rules; 
 wherein said subject is a patient to be diagnosed. 
 
     
     
       3. A method according to  claim 2 , wherein said step iii) comprises extracting rhythm features from said ECG signal record for defining an initial AEA-wave search window. 
     
     
       4. A method according to  claim 2 , wherein said step iii) comprises creating a linear combination of eight lead signals, thereby obtaining an emphasized AEA signal. 
     
     
       5. A method according to  claim 1 , for detecting fetal distress in a pregnant woman by non-invasively measuring ECG signals of said woman, wherein:
 step i) comprises providing an ECG signal record consisting of 4-12 lead signals produced by the hearts of said pregnant woman and a fetus; 
 step iii) comprises identifying in said ECG signal record the electrical activity associated with fetal QRS complex (fQRS); 
 step iv) comprises determining parameters α and β in a fetal ECG signal; and 
 step v) comprises assigning to the combination of said parameters α and β of step iv) a state of fetus according to the clinically oriented set of rules. 
 
     
     
       6. A method according to  claim 5 , wherein said step iii) comprises enhancing a fetal ECG source signal using a linear combiner and a synthetic fetal QRS signal. 
     
     
       7. A system for detecting and classifying cardiac arrhythmias in an ECG signal record, comprising
 i) means for measuring ECG signals produced by the heart of a human subject comprising electrodes for detecting a potential difference at a plurality of points on the skin of said subject during a predetermined time interval, providing 12 lead signals; 
 ii) filtering means for removing noises outside a frequency range of 0.5 to 49.5 Hz; 
 iii) a detector for resolving a QRS complex in said ECG signal record; 
 iv) means for creating a synthetic signal and a modified linear combiner for resolving a peak of atrial electrical activity (AEA) in said ECG signal record; 
 v) means for determining parameters α, β, γ, and δ in said ECG signal record, wherein α is R-R regularity, β is HR, γ is a position of AEA wave relative to the QRS complex in said ECG signal record, and δ is a ratio of the AEA wave and the QRS complex; and 
 vi) software means for assigning to a combination of said parameters α, β, γ, and δ of step v) an arrhythmia type according to a clinically oriented set of rules, and for outputting the results. 
 
     
     
       8. A system for detecting fetal distress in a pregnant woman, comprising:
 i) means for measuring ECG signals produced by the heart of said woman and of the fetus to provide an ECG signal record, comprising electrodes for detecting a potential difference at a plurality of points on the skin of said woman during a predetermined time interval, providing at least 4 lead signals; 
 ii) filtering means for removing noise from said ECG signal record outside a frequency range of 0.5 to 49.5 Hz; 
 iii) means for creating a synthetic signal and a modified linear combiner and a detector for resolving fetal QRS complex (fQRS) in said ECG signal; 
 iv) means for determining parameters α and β in said ECG record, wherein α is R-R regularity and β is HR in a fetal ECG signal; and 
 v) software means for assigning to a combination of said parameters α and β a fetal state.